#include <bits/stdc++.h>
#include "race.h"
#define fi first
#define se second
#define maxn 1000
#define pb push_back
using namespace std;
typedef pair<int,int> pi;
int n,k,ans;
vector<pi> adj[maxn];
void dfs(int u , int dad , int d , int dist) {
if(dist == k)
ans = min(ans,d);
int deg = adj[u].size();
for( int i = 0 ; i < deg ; i++ ) {
int v = adj[u][i].fi;
int dist2 = dist + adj[u][i].se;
if(v != dad)
dfs(v,u,d+1,dist2);
}
}
int best_path(int N, int K, int e[][2], int c[]) {
n = N;
k = K;
ans = n+1;
for( int i = 0 ; i < n-1 ; i++ ) {
int u = e[i][0];
int v = e[i][1];
int d = c[i];
adj[u].pb(pi(v,d));
adj[v].pb(pi(u,d));
}
for( int i = 0 ; i < n ; i++ )
dfs(i,-1,0,0);
return (ans < n) ? ans : -1;
}
